Amplifier Profit Margin Distortion

Hello again kids. It’s time to lance another of my favorite audio hot air balloons (notice I stayed away from the zit metaphor out of consideration for you gentile reader). Today we will answer the questions:

  • How much power do I need?
  • Which is better: Tubes or Transistors?
  • How much do I need to spend?

Let’s start with the how much power do I need part.

We need to go back and take another walk around your listening room.

The size of your room and the speakers you have selected are the two things we need to discover.

The larger your room (and the farther you sit from your speakers when you listen) is of primary interest. A typical bedroom for example should never require more than about 100 watts RMS (total of two channels) even with inefficient acoustic suspension speakers. This assumes an “honest” low distortion 100 watts RMS over the audible frequency range. RMS stands for “Root Mean Square” which simply means it can supply the power for any possible musical material. And yes, rock is usually more demanding on average but classical is usually more demanding for peaks. RMS power can handle either situation. And by “low distortion” we usually look for no more than 0.1% at full power output. And it must be able to supply this “honest” 100 watts over the entire range of hearing (unless you are a dog in which case you will need to pay more for an amp that will cover the ultrasonic frequencies we can’t hear).

originalnipper

But what about volume? What if I like my Led Zeppelin cranked to 11? 

Whoa. Back up the bus. What’s the goal here? To paint the audio illusion that you are there or they are hear in a way that can not be distinguished from the original. As discussed, unless a rock band is recorded live (you would definitely be there) it is most unlikely there was an “original” to emulate other than what came out of the studio monitors when the recording was made. And the sound pressure levels at a rock concert is subject for another blog (and another set of ears to damage thank you verry much).

An acoustic orchestra or a vocalist with an ensemble is something which can be reproduced because it was actually produced. And it is this which the honest 100 watts can provide in your 10 x 16 bedroom with startling authenticity.

But what if I have very efficient speakers? Won’t I be better off with an amplifier with a lower power rating?

Nah. That’s what the volume knob is for. Set it on 4 instead of 8.

Okay, what about my living room which is much larger?

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How much larger? This is where things can get expensive. Your ears don’t play fair when it comes to loudness. In theory, to make an instrument or vocalist sound twice as loud, (or sound the same except from twice as far from the speakers), a ten fold increase in amplifier power is needed. This assumes your speakers can handle this much power. So 100 watts suddenly becomes 1000 watts.

But wait! There’s good news! Remember the listening room you just built a few entries back? It has walls and a floor and ceiling which always reflect some of the sound to your ears. And there is another really good thing about your brain to keep in mind. We have a hard time remembering exactly how loud something was originally. So the naked truth is, if you get the sonic details correct (directionality, frequency range, tonal balance, waveform integrity, dynamic range, all the responsibility of the guy behind the glass), and you have taken care to properly play his product (on your choice of sources / more about these in coming chapters), and your speakers are capable of faithfully following the electrical power your amplifier is working so hard to send to them, the actual sound pressure level (volume) is not a deal breaker. All will be well in the land of audio reproduction. The musicians will be magically transported to here or you to where they are.

In a large family room or living room even with relatively inefficient speakers, 500 watts RMS total of 2 channels (with the same assumptions discussed previously) is more than enough for any real world acoustic material.

So which is better, tubes or transistors?

Yes.

Either.

There is no better (or worse). Only more or less accurate. And accuracy can be scientifically quantified.

An amplifier has only one job. Gain. A perfect amp will take a “small” musical waveform and make it much “larger”. That’s all. It will not add or subtract or in any way change anything except “size”. Transistors and tubes are devices which allow us to do this. Neither is perfect. They both contribute subtle changes to the waveform. But as long as their contributions are within objective measurable (distortion) limits, it does not matter.

So how much should I spend for a 500 watt amp?

You should buy (spend) whatever you want and can afford on an amp that makes you happy. That’s  a different question from what do I need to spend for an amp that will bring them here or me there. That’s where profit margin distortion comes in. There are some very nice folks that will sell you a spiffy new amp with any imaginable feature. And damn are they pretty. So go for it if it makes you happy and your checkbook is up to the task.

But truth be told, spending more than about two bucks a watt is just not necessary in order to have a convincingly life like copy of Yo Yo Ma playing cello in your listening room.

Next time: What’s All the Vinyl Hoopla About?

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Speakers 101 – Part 2

It’s tough sometimes to carry the blog banner “Just the Facts”. Yeah I can be a bit pompous but is arrogance really arrogant when one is accurate and spot on about something? An athlete can trash talk and it’s just hype PR unless he delivers the goods. You get my drift. So what has any of this to do with speakers?

I humbly submit an article by the prestigious audiophile bible “The Absolute Sound”. It identifies the 12 most significant loudspeakers of all time. They range from absurdly esoteric and outrageously expensive models to ones that grace untold millions of wonderful economical home systems. Just as a reality check: I own and use #2 & #10 to listen to music in my home.

So is this ultimate proof? Are these the only ones to consider? Of course not. Remember my advice when going to pick out a speaker systems? Go and listen to some live music first. Then select the speaker that makes a quality recording of similar material sound most convincing and life like keeping in mind your listening room and available amplifier power. And don’t be duped by audiophile hype about some absurd new principle that rewrites the laws of physics.

That’s it folks. Just the facts…

Rustoleum

Neil Young has more money than God. And he has an army affectionately known as “Rusties” after his 1979 album “Rust Never Sleeps”. And when Neil takes a stand on a subject, a lot of these folks stand up and salute. Now Mr Young is well known for his position on social issues and let me be listed among those that admire his work in such endeavors. But as well intentioned as he may be, he has now run afoul of “The Naked Audiophile” by introducing a new audio format he refers to as “Pono”.

From his website:

Pono means righteous. It is a Hawaiian word, the one, the pureness. On behalf of Pono, we thank you for helping us give music a voice. You have helped to set the stage for a revolution in music listening. Finally, quality enters the listening space so that we can all hear and feel what the artists created, the way they heard and felt it.

This is done when the artist makes the best available, wanting to share it with you. It happens when the artist lets you hear and feel more than what is on your CD or MP3 of any song. CDs and MP3s are derived from the original masters, and now, with the PonoPlayer, you can finally feel the master in all its glory, in its native resolution, CD quality or higher, the way the artist made it, exactly. That’s the beauty of Pono.

It’s been a long time coming. It was not easy getting this far, but you made it happen by supporting Pono’s vision for better listening. We have been working with the labels, with the artists and producers, and we will continue to do that. We go to the source to find the best and bring it to you. Pono wants to preserve the history of music, in all of its beauty and expression, for all time. Forever.

There is a way to do this right, and we are going to do it. We will be sharing how we will do this with you over the next few months, while we build your first ever PonoPlayers. We are going to do some revolutionary things. We will make music available in a way that has never been done, a way that allows for constantly attaining the best listening experience.

Thank you to the artists, the recording companies, big and small, and most of all, thanks to you music lovers for making this happen with your amazing support.

Thanks for listening,

Neil Young

OK. Huh? What did he say?

Well first I have to “Pony” up $400 for his proprietary player. I guess I don’t want to miss out on such a revolutionary leap in audio technology. But then, I have to buy all new tracks which have been specially processed in high resolution in order to experience this audio bliss. And even though the Pono player will play my lossless WAV or FLAC files, they are apparently not high enough resolution. And all my MP3 files? Well certainly they are out of the running.

This may be a good time to discuss all this hu ha about lossless files and compression and digital Vs. analog. I could fill a book with the latter question alone. But my role here is to cut to the chase and give my vast and well deserved audience just the facts. So once again I will resort to my old friends the factoids:

Factoid #1: It can be scientifically shown that there is no audible difference between music recorded digitally using high rate / high quality compression (such as MP3’s or Pono) and lossless formats such as WAV files. What’s the more, once you digitally divide a waveform into fine enough parts, and have enough storage to keep them and play them back accurately, it effectively becomes a perfect analog copy. It makes engineers really nervous when you tell them that everything is really analog anyway. They turn blue and jump up and down.

Factoid #2: Read factoid #1 again out loud. And no jumping or turning blue. Here is an excerpt from a beautifully written article by Brent Butterworth over atAudiophile Review which helps to make this point clear:

Many audio enthusiasts describe the effects of MP3 much as they would describe the effects of dubbing audio onto analog tape, which has a deleterious effect on almost every aspect of audio quality (frequency response, dynamic range, signal-to-noise ratio, distortion, etc.). It doesn’t work that way. It’d be more useful (although not literally accurate) to think of MP3 and other lossy codecs as introducing random elements. The lower the bitrate (i.e., 128 kbps vs. 256 kbps), the more random elements are introduced, and the lower the audio quality. The frequency response and dynamic range are essentially unchanged, there’s just more junk in the signal.

That’s because MP3 works not by reducing dynamic range or frequency response, but by discarding data that’s less likely to be heard. It breaks an audio sample down into multiple frequency bins; analyzes them to find out sounds that are unlikely to be heard (for example, a 1.1 kHz tone at -20 dBFS adjacent to a 1 kHz tone at -3 dBFS); then reduces or zeroes-out the number of bits used to encode those relatively inaudible tones. You’ll still hear that loud -3 dBFS tone in almost all of its original glory, minus or plus the slight level error that MP3 might introduce. Of course, that’s a greatly simplified explanation; if you want to dig deeper, try this site.

Here’s another way to think about it. Imagine the audio signal as a wall-size painting. Then think of MP3 as a kid with a BB gun. If the kid starts shooting the picture in random places with the BB gun, and you’re viewing the painting from 20 feet away, you probably wouldn’t notice the first few holes. As dozens of holes appear, you’d eventually start to notice them, but the overall content of the picture would remain unchanged – the color would appear the same, the black and white levels would appear the same, and the objects depicted would still be easily recognizable.

By the time the kid empties the entire 650-shot magazine of his Red Ryder, parts of the painting might be missing enough canvas that its colors and shades start to shift, and certain elements pictured in the painting become unrecognizable. That would be roughly analogous to encoding MP3 at 32 kbps, as compared to the 128 kbps I’ve used here and the 256 kbps bitrate now used for most commercially distributed MP3 downloads.

– See more at: http://audiophilereview.com/cd-dac-digital/how-much-does-mp3-affect-dynamic-range.html#sthash.MMogKVY8.dpuf

So Mr. Young, the emperor has no clothes. And, if as all the Rusties out there contend, your Pono files do sound “better” (whatever that means), it is not because of the Pono format, but because the man behind the glass is paying more attention when the boss is in the studio.

And who knew Rustoleum works so well on rusty audio files as well as rusty audiophiles?

Oooh so sorry…

Speakers 101

Speakers 101

OK kids it’s (finally) time for what you all have been waiting for: the naked truth about speakers. I will probably make some enemies and lose some readers here. But so be it. Let’s start out by reviewing the goal of this blog: “To discuss producing, in a home environment, a sound field which is indistinguishable from the original live acoustic musical performance from which it was recorded”.

That’s important because if your goal is something other than this, what I have to share here may not be very helpful.   We have already spent some time discussing the space where your speakers will reside. For now I’ll limit my discussion to a classic 2 speaker (system) stereo in front installation. Speakers 101 is a prerequisite for Speakers 102, 103, 104 etc where we might cover more exotic installations. But we first need to understand some basic characteristics that a speaker system needs in order to convince you that “you are there” or “they are here”. This does not mean “better” or “worse” sounding. Those are subjective. The Holy Grail here is accuracy: A sound field which is indistinguishable from the original performance. We are out to deceive your brain. Audio sleight of hand.

A few starters:

 Factoid #1: Audio is not wine, people. There is nothing a speaker does that can not be scientifically measured in such a way to give a real picture of its ability to accurately generate a sound field in a given environment using the original performance as a basis of comparison. If one prefers to make measurements by virtue of biological transducers (listening with our ears), a “double blind” test is a perfectly acceptable substitute.

Factoid #2: A perfect copy of the original sound field is not required in order to be completely convincing. Thank your aboriginal brain for this. A few years ago Acoustic Research decided to do some marketing promotions where they invited listeners with all levels of expertise to a concert which featured a stage and musicians along with a pair of AR3’s which were, at the time, their best loudspeakers. The musicians would play a passage live and at some point stop at which time a recording of the same musicians (done in an anechoic environment) was fed through the loudspeakers. The listeners were then asked to identify the live Vs. recorded passages. Can you guess what the listener’s responses were? Some said they could identify a subtle difference in the sound between the two passages but were unable to come to a consensus of which were live and which were recorded. Howcum? Our brain has a poor ability to recall the details of a sound out of context. We can identify the roar of a saber toothed tiger. But the timbre or articulation of his roar is not relevant for survival. No different with a cello or piccolo. We can identify them. But beyond that it becomes tres difficult. More on this later. I digress. Suffice it to say that a perfect audio copy of what is being fed to the speaker, while very preferable, is not a requirement.

Factoid #3: The laws of acoustics (physics) have not been repealed. There are a ton of manufacturers out there that claim their stratospherically priced products incorporate some new technology which makes all previous designs obsolete. Hokum. You are certainly entitled to buy what ever it is that floats your boat. But be advised, there is no connection between how a speaker system looks and how accurate it is. Um, well, maybe there is a little connection. The more a speaker system looks like a sculpture or a space ship, the less likely it is to be accurate. And the more likely it is to empty your wallet.

     Factoid #4: The number of drivers (speakers) in a system is a poor indicator of accuracy. Indeed the old engineering axiom which instructs us that simpler is (almost always) better is very much in keeping here. The only things of importance to be convincing are how smooth and to a smaller extent how wide the overall frequency response is, how linear the dynamic range is over the loudness required for the material in the given listening space, and the uniformity of the spatial dispersion pattern.

 Factoid #5: There are many ways to arrive at the same metaphorical place. Speaker systems use many different driver and enclosure designs. They all work to one degree or another. Some better than others. From a purely theoretical perspective, they all seek to emulate a mass less pulsing sphere: an isotropic (point) source which radiates a wave front of any audible frequency equally in all directions. But who cares? Which is the best design and manufacturer and model? How do I tell? This brings us back to Factoid #1. By looking at the “specs” , one can determine the best choice. But a trip to your local audio purveyor is so much more fun. So let’s go. Really. Not to worry. We’ll do this together.

OK. But before we go speaker shopping though, we need to have a look at our listening room. Important things to consider are how large is your room, and how much amplifier power do you have available to drive your new speakers? The larger the room or the less power you have, the more efficient your speakers must be to provide the volume necessary to be convincing. That is, they must make your music louder than other speakers of less efficient designs. Some examples of efficient speaker designs are “horns” or direct radiators (traditional speaker cones) in a “bass reflex” (ported) enclosure.   If on the other hand, you are the happy owner of an amplifier or receiver that provides a robust amount of available power, or your listening room is modest is size, a less efficient speaker system may be your best choice. An “acoustic suspension” design will provide a powerful and accurate low end but will require more power to deliver a realistic sound pressure (volume). And it will do this from a relatively small enclosure. Which design is better for your system will depend on these issues.   In any case, our new speakers must also have a uniform dispersion pattern which means the sound level remains as uniform as possible over a 180 degree hemispheric pattern. This is especially important (and difficult) at the high frequency end of the spectrum. And / yes / this too can be measured and quantified.   Oh, and one more thing, the night before you go to the audio salon, go listen to some live music. It should be similar to what you will be playing at home, preferably a small acoustic instrumental or vocal ensemble. Remember what we said back in factoid #2 about our acoustic memory? It will help you to identify the most accurate speaker. Believe it. Only the facts here…

To be continued…

The Second Most Important Audio Component

Back thataway several posts I opined that the most important component in your audio system is the recording engineer responsible for capturing the original musical performance. It’s a fact, kids. So now what’s next? Surely it’s time to think about D to A converters, or low distortion speaker cables made only with organic oxygen free copper, or yada yada yada. Nope. The second most important audio component in your system is your listening room.

Since the goal is (repeat again after me) to produce the most believable sonic image of the original, we need to be able to transmit this sound to your ears from your speakers in the most accurate and uncolored way possible. This means we need to keep from adding or subtracting any sound levels that were not part of the original. The truth is, our ears are not too smart. But our brains will instantly call fowl if the spectral balance is messed up.

So how do we go about dealing with this? There are several things to consider about the room (and the space within it) which will have a huge effect upon how convincing the sonic image is to our brains. Let’s take them one at a time.

First, we need to understand a bit about room acoustics. Walls are required in most rooms. Sonically they can do good things or bad things. Which they do depends upon their construction, dimensions, and placement relative to one another. I will spare you the math associated with how to answer this question in favor of some general do’s and don’ts:

  • Parallel walls are bad;
  • Curved or non parallel walls are good;
  • Sloping ceilings are good;
  • Sloping floors are good for sound but can be dangerous;
  • Avoid a room where walls (including the floor and ceiling) are equal or multiples Eg: 10x10x10 is the worst possible; 10x20x10 is nearly as bad;
  • Having large heavy objects in the room is good (unless they are the listener);
  • Walls should be rigid. 16″ on center studs and drywall is not a wall at 40 Hz;
  • Room size is also dependant upon your speakers and available amplifier power. More on this later too;

OK Second, we need to determine the optimal location for your speakers. The distance between your speakers and a rigid surface (such as a wall or floor) will have a big effect upon bass response. Um, no. The speakers will respond almost the same no matter where you put them. What I should say is, it will have a big effect on how loud and the how smooth the bass sounds to you depending upon where your ears are in the room. Again there is a ton of math you can use to determine this but for most folks there are practical considerations about where your speakers end up in your home environment (such as marital bliss). So more do’s and don’ts:

  • Putting speakers deep in corners of the room is very bad. It’s scary in there for them;
  • Sitting on the floor is bad (if you are a speaker);
  • Speakers need some distance between them. For now let’s just consider a classic 2 channel stereo system.  A good starting point is the distance between them should be roughly the same as the distance to your ears;
  • Let your speakers away from the wall. They like to join the party;
  • Try to maintain an equal distance between each speaker and an adjacent wall. Symmetry is good;

Remember: All this is primarily about the bass reaching your ears. For a simple classic two speaker system, it matters not how much you spend on “technology”. No amount of equalization will cure a bad listening room acoustic problem. The uniformity of  amplitude across the low end of the spectrum as well as the absolute low frequency limit will both be highly influenced by the room shape, construction, contents, where you are, and where your speakers are in it. This is laws of physics folks. Get used to it.

Middle and high frequencies are a different problem for room design. They react to their surroundings in quite a different way from the low end. Bass energy tends to go through surfaces easily. Middle and especially high frequencies are easily reflected by hard surfaces and much more readily absorbed especially by soft materials such as rugs or drapes. In general, at least some broad surfaces should have damping (rugs, drapes, wall hangings). The exact amount of these soft acoustically absorbent materials will depend upon your speakers and the size of the room. Too much softness and the sound will lack openness and sparkle. Too little softness will mean unpleasantly bright and hollow audio. Given the right balance, the sound from the loudspeakers will reach your biotransducers (ears) in tact and with the least amount of coloration from your listening room. Listening trial and error will carry the day on this one.

Next time: Speakers 101